Alternate fuels have been identified to mitigate the rising price of conventional energy sources and environmental concerns. For example, alcohol has been recognized as an attractive alternative source of energy, and more particularly a fuel for automotive applications. Various engine systems may be used with alcohol fuels, utilizing various engine technologies such as turbo-chargers, super-chargers, etc. Further, various approaches may be used to control alcohol-fuelled engines with such devices, including adjustment of boost or spark timing in dependence upon an alcohol content of the engine fuel, and various operating conditions.
The inventors herein have recognized several interrelated issues with alcohol-fuelled engines involving the fuel delivery system, and found that it is possible to operate the engine system to achieve improved engine performance with an alcohol fuel or blend by varying the amounts, timing, and/or number of injections in a cycle.
In this way, it is possible to utilize direct injection, along with an appropriate boost, spark, and fuel control system, to take advantage of increased charge cooling effects via alcohol's higher heat of vaporization and increased octane to provide an engine with improved peak torque output and/or emission performance.